My 2004 E 320 electronic key wont turn in the ignition to start car. it seems to be locked

You've probably gotten this taken care of by now, but if not, does your key unlock/lock the doors? If no then your key battery is probably dead and needs to be replaced. Also, sometimes if your front wheels are turned to sharply it will make turning the key very difficult. Insert your key and you should hear a clicking noise that lets you know the key is recognized by your E320, then try and move the steering wheel to the left or right with some force and the same time you are trying to turn the key to the on position, and if that was the issue the key will now turn.